CN102901672B - Test method for researching transformation mechanism of martensite in austenitic stainless steel - Google Patents
Test method for researching transformation mechanism of martensite in austenitic stainless steel Download PDFInfo
- Publication number
- CN102901672B CN102901672B CN201210397613.4A CN201210397613A CN102901672B CN 102901672 B CN102901672 B CN 102901672B CN 201210397613 A CN201210397613 A CN 201210397613A CN 102901672 B CN102901672 B CN 102901672B
- Authority
- CN
- China
- Prior art keywords
- stress
- sample
- martensite
- stainless steel
- load
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Landscapes
- Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
Abstract
The invention discloses a method for researching the transformation characteristic of martensite in deformation strengthening austenitic stainless steel in a low-temperature environment. The method comprises the following steps of: performing a stress-applied creep test and a constant-strain relaxation test on an austenitic stainless steel material in the low-temperature environment; and acquiring the transformation mechanism of the martensite in the deformation strengthening austenitic stainless steel in the low-temperature environment by a stress relaxation curve and a sample deformation curve. The problem that research on the transformation mechanism of the martensite by applied stress or strain under the condition of sufficient degree of supercooling does not exist in the prior art is solved; and the method is simple and effective and is used for testing the transformation mechanism of the martensite under the condition of stress or strain in the low-temperature environment, provides technical support for manufacture of the austenitic stainless steel for a deformation strengthening pressure vessel in the low-temperature environment, and has quite important value and significance on research of the transformation mechanism of the martensite in the austenitic stainless steel in the low-temperature environment.
Description
Technical field
The present invention relates to the test method of transformation mechanism of martensite in working hardening austenitic stainless steel under a kind of novel test low temperature environment, is more particularly a kind of method adopting transformation mechanism of martensite in working hardening austenitic stainless steel under creep test technique study low temperature environment.
Background technology
Stainless steel has good decay resistance, excellent moulding, toughness, weldability and cold-forming property, is widely used in the pressure vessel and equipment (comprising fixed and transportable pressure vessel, heat exchanger etc.) in the industrial circles such as oil, chemical industry, nuclear power.But as 304 stainless steels also exist, intensity is not high, anti-stress corrosion performance is poor, and intercrystalline corrosion sensitivity is comparatively large, and there is the shortcomings such as martensitic traoformation in cold working process, limits its application.In design of pressure vessels and manufacture process, because 304 stainless steel yield strengths of solution annealing are very low, substantially at about 220MPa, cause the design wall thickness of pressure vessel very thick, substantially increase material cost, peter out in resource, under the situation that material price rapidly goes up, solution annealing state 304 Stainless steel pressure vessels manufacturing cost has exceeded the ability to bear of many industries.Therefore, development new technologies and the original technology of improvement, existing production technology is sought new technique processing method to improve its yield strength, just reduces production cost by reducing product thickness, thus greatly accelerate pressure vessel industries development, drive chemical industry leap.
The method of traditional raising austenite stainless hardness of steel comprises solution strengthening and precipitation-hardening etc., but said method also will make basic steel grade change while the raising strength of materials.Refined crystalline strengthening is also improve a kind of means of austenite stainless hardness of steel, but goes back imperfection to the research of the method at present.Method proper at present adopts strain hardening technology.Stainless steel working hardening comprises Room Temperature Deformation strengthening and low temperature deformation strengthening, and its mechanism, method, technique have quite poor other.These factors must be considered in design of pressure vessels manufacture.
The working hardening of Stainless steel pressure vessels is generally that the material of annealing is first manufactured pressure vessel through welding, then makes rustless steel container that deformation occur under high effect of stress through hydraulic pressure or cryogenic liquid pressurization or produce strain-induced martensite thus the permissible stress of raising container material.Container under normal temperature makes container produce the plastic yield of about 3-5% by hydraulic pressure way, the martensite produced in this process is considerably less, the mechanism of strengthening can think that plastic yield is strengthened, and at low temperatures or the larger situation of deformation degree, just must consider the impact of martensite transfor mation.At this moment the transition mechanisms of martensite under stress and low temperature must just be considered, according to the requirement of pressure vessel permissible stress design, different hydraulic levels is adopted to obtain the martensite content needed, thus reach the object of hardened stainless steel container, if adopt stress unreasonable, cause martensite generation fulminant to change, scrapping of pressure vessel will be caused, cause serious financial consequences to enterprise, or bring very large security risk to user.Because under research liquid nitrogen temperature, working hardening pressure vessel austenitic stainless steel relates to above-mentioned situation in manufacture process, therefore martensite transfor mation characteristic in working hardening 304 stainless steel must to be studied under liquid nitrogen temperature, for the manufacture strengthening austenitic stainless steel pressure vessels provides technical support.So it is necessary to invent a kind of test method studying transformation mechanism of martensite in working hardening austenitic stainless steel under low temperature environment.
Summary of the invention
The object of the invention is for the problems referred to above, provide a kind of and adopt creep test method, martensitic transition mechanisms in working hardening austenitic stainless steel under research low temperature environment.This method can find the transformation mechanism of martensite under low temperature environment and stress act on simultaneously, obtains martensite transfor mation speed, under low temperature environment, the manufacture of working hardening austenitic stainless steel pressure vessels is provided fundamental basis.
The present invention is achieved by the following technical solutions:
Study a test method for transformation mechanism of martensite in austenitic stainless steel, it is characterized in that, described test method comprises stress relaxation test under low temperature environment and deformation of creep test, tests and carries out on electro-hydraulic servo universal testing machine,
Stress relaxation test under described low temperature environment comprises the steps:
I. sample 3 is contained in cryostat, 5, pours liquid nitrogen into, and the temperature of the liquid nitrogen in cryostat, 5 measured by thermopair 2;
II. according to the cross sectional dimensions of sample 3, getting proof stress is (20% ~ 90%) σ
sthe yield strength of material (under the test temperature), according to formula " load=stress × specimen cross sectional area ", calculate the load corresponding to proof stress respectively, by the fine setting of testing machine 1, sample 3 is loaded on required load, keeps piston 4 invariant position;
III. observe load (or stress) over time, and record load-time curve;
Deformation of creep test under described low temperature environment comprises the steps:
I. sample sample 3 is contained in cryostat, 5, pours liquid nitrogen into, and the temperature of the liquid nitrogen in cryostat, 5 measured by thermopair 2;
II. according to the cross sectional dimensions of sample 3, getting proof stress is (70% ~ 90%) σ
sthe yield strength of material (under the test temperature), according to formula " load=stress × specimen cross sectional area ", calculates the load needed for proof stress respectively, by the fine setting of testing machine 1, sample 3 is loaded on required load, keep load constant;
III. observe distortion over time, and record sample deformation-time curve;
Wherein:
Described low temperature environment is-196 ~-80 DEG C, and described sample 3 is austenite stainless steel curved beam.
In described test method, the preferred diameter of sample 3 is the standard tensile specimen of Φ 6mm.
Beneficial effect
The invention has the beneficial effects as follows: by creep test method, applied stress or strain in enough degree of supercooling situations, the martensite transfor mation characteristic in working hardening pressure vessel austenitic stainless steel under low temperature environment can be studied, to disclose under low temperature environment and stress or strain acting in conjunction transformation mechanism of martensite in austenitic stainless steel.Can be found by method of the present invention: plus load can not cause the increase of martensite nucleation speed in the short period of time, martensite transfor mation can only be carried out with very low rate; Under effect of stress, after incubation period after a while, martensite transfor mation speed is accelerated suddenly, completes, belong to the category of explosive martensite transfor mation within the very short time.
Present method solves in research in the past the problem substantially not relating to applied stress or strain research transformation mechanism of martensite under enough degree of supercoolings, provide the transition mechanisms of martensite under stress or strain under a kind of simple, effective method test for low temperature environment, under low temperature, the manufacture of working hardening pressure vessel austenitic stainless steel provides technical support.
Accompanying drawing explanation
Fig. 1 is low temperature environment creep test platform.
Wherein, 1: testing machine, 2: temperature instrumentation, 3: sample, 4: piston, 5: cryostat.
Fig. 2 is the stress relaxation curve under 304 stainless steel liquid nitrogen temperatures.
Fig. 3 is the deformation of creep curve under 304 stainless steel liquid nitrogen temperatures.
Embodiment
Stress relaxation test under embodiment 1304 stainless steel liquid nitrogen temperature
As shown in Figure 1, low temperature stress relaxation test method of the present invention is carried out on electro-hydraulic servo universal testing machine 1, and sample 3 is 304 stainless steels, and concrete test procedure is as follows:
I. sample 3 is contained in cryostat, 5, pours liquid nitrogen into, and the temperature of the liquid nitrogen in cryostat, 5 measured by thermopair 2, and liquid nitrogen temperature controls at-196 DEG C;
II. according to the cross sectional dimensions of sample 3 (diameter is the pole sample of Φ 6mm), according to formula " load=stress × specimen cross sectional area ", calculate the load of proof stress needed for 100MPa, 300MPa, 500MPa, 700MPa respectively, by the automatic control program of testing machine 1, in 30 seconds, sample 3 is loaded on required load, keeps piston 4 invariant position;
III. observe stress over time, and record stress time curve, test findings is shown in Fig. 2;
As can be seen from Figure 2, no matter stress level how, load in the early stage (in one minute) has and comparatively significantly declines, then the decline of load and the time substantially linear, and the slope that the load under all stress levels declines is substantially identical, show that plus load does not change the forming core speed of martensite transfor mation.The stress of 700MPa, close to the yield strength of 304 stainless steels under liquid nitrogen temperature, be bound to cause many crystal grain generation slippages in austenite structure, but stress level high so does not cause the acceleration of martensite transfor mation.This is all unaccountable by homogeneous nucleation and heterogeneous nucleation theory.Can draw thus, under so high degree of supercooling, the atom action degree needed for martensite nucleation obviously declines, even if applied stress also cannot make martensitic forming core speed increase in the short period of time.Under general condition, the time plays a part minimum in martensite transfor mation process, and when the temperature greatly lower than zero degree, the time just becomes important technological factor.With this, plus load can not cause the increase of forming core speed in the short period of time, and in austenitic stainless steel, martensite transfor mation can only be carried out with very low rate.
Deformation of creep test under embodiment 2 304 stainless steel liquid nitrogen temperature
Test unit used in this example, specimen types are identical with embodiment 1, and difference is that in the method, test load remains unchanged, and concrete steps are as follows:
I. sample 3 is contained in cryostat, 5, pours liquid nitrogen into, and the temperature of the liquid nitrogen in cryostat, 5 measured by thermopair 2, and liquid nitrogen temperature controls at-196 DEG C;
II. according to the cross sectional dimensions of sample 3 (diameter is the pole sample of Φ 6mm), according to formula " load=stress × specimen cross sectional area ", calculate the load of proof stress needed for 500MPa and 600MPa respectively, by the automatic control program of testing machine 1, in 30 seconds, sample 3 is loaded on required load, keeps load constant;
III. observe sample deformation over time, and record sample deformation-time curve, test findings is shown in Fig. 3;
304 stainless deformation curves can be divided into three phases according to Fig. 3.First stage, and relaxation test is similar, is out of shape linear in time, show and occur very low martensite transfor mation speed under effect of stress, under 500MPa stress, this phase duration reaches effect in 90 minutes, and under 600MPa effect of stress, the duration is only 40 minutes., there is fulminant martensite transfor mation in subordinate phase, in the short period of time (5-10 minute) under effect of stress, and martensite produces in a large number, accounts for more than 80% of total martensite transfor mation amount.Phase III, martensite transfor mation speed obviously reduces, lower than or close to the rate of transformation of first stage.This explanation 304 stainless steel low-temperature martensite transition mechanisms under effect of stress are different from the transformation mechanism of martensite under unstress state completely.At unstress state; martensite transfor mation belongs to isothermal martensite and changes; although along with the increase of time; martensite transfor mation speed first increases rear slack-off; but the increase of its speed relaxes very much, and under effect of stress after incubation period after a while, martensite transfor mation speed is accelerated suddenly; complete within the very short time, belong to the category of explosive martensite transfor mation.
Claims (2)
1. study a test method for transformation mechanism of martensite in austenitic stainless steel, it is characterized in that, described test method comprises stress relaxation test under low temperature environment and deformation of creep test, tests and carries out on electro-hydraulic servo universal testing machine,
Stress relaxation test under described low temperature environment comprises the steps:
I. sample (3) is contained in cryostat, (5), pours liquid nitrogen into, and the temperature of the liquid nitrogen in cryostat, (5) measured by thermopair (2);
II. according to the cross sectional dimensions of sample (3), getting proof stress is (20% ~ 90%) σ
saccording to formula " load=stress × specimen cross sectional area ", calculate the load corresponding to proof stress respectively, by the fine setting of testing machine (1), sample (3) is loaded on required load, keeps piston (4) invariant position;
III. observation load or stress are over time, and record load-time curve;
Deformation of creep test under described low temperature environment comprises the steps:
I. sample (3) is contained in cryostat, (5), pours liquid nitrogen into, and the temperature of the liquid nitrogen in cryostat, (5) measured by thermopair (2);
II. according to the cross sectional dimensions of sample (3), getting proof stress is (70% ~ 90%) σ
s, according to formula " load=stress × specimen cross sectional area ", calculate the load needed for proof stress respectively, by the fine setting of testing machine (1), sample (3) be loaded on required load, keep load constant;
III. observe distortion over time, and record sample deformation-time curve;
Wherein:
Described low temperature environment is-196 ~-80 DEG C, and described sample (3) is austenite stainless steel curved beam.
2. the test method studying transformation mechanism of martensite in austenitic stainless steel as claimed in claim 1, is characterized in that, the standard tensile specimen that in described test method, sample (3) is diameter of phi 6mm.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201210397613.4A CN102901672B (en) | 2012-10-18 | 2012-10-18 | Test method for researching transformation mechanism of martensite in austenitic stainless steel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201210397613.4A CN102901672B (en) | 2012-10-18 | 2012-10-18 | Test method for researching transformation mechanism of martensite in austenitic stainless steel |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN102901672A CN102901672A (en) | 2013-01-30 |
| CN102901672B true CN102901672B (en) | 2015-03-04 |
Family
ID=47574029
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201210397613.4A Active CN102901672B (en) | 2012-10-18 | 2012-10-18 | Test method for researching transformation mechanism of martensite in austenitic stainless steel |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN102901672B (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104820012B (en) * | 2015-04-03 | 2018-07-06 | 合肥通用机械研究院有限公司 | The lossless detection method of martensite transfor mation amount in a kind of austenitic stainless steel |
| CN109933815B (en) * | 2017-12-15 | 2022-12-02 | 天津大学 | Creep induction period prediction method for coupling residual stress and constraint effect under steady-state creep condition |
| CN109933822B (en) * | 2017-12-15 | 2022-11-04 | 天津大学 | Creep induction period prediction method considering load-independent constraint parameters under plastic transient creep condition |
| CN109777936B (en) * | 2019-02-26 | 2020-11-20 | 东南大学 | Ultra-low temperature strain strengthening method for martensitic stainless steel |
| CN111996347A (en) * | 2020-07-29 | 2020-11-27 | 天津大学 | Method for strengthening austenitic stainless steel through low-temperature circulating strain after room-temperature pre-strain |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE69713446T2 (en) * | 1996-04-26 | 2003-08-07 | Denso Corp | Process for stress-induced transformation of austenitic stainless steels and process for producing composite magnetic parts |
| CN102645377A (en) * | 2012-04-19 | 2012-08-22 | 中国科学院理化技术研究所 | Fatigue property test device of 4.2-300K temperature area |
-
2012
- 2012-10-18 CN CN201210397613.4A patent/CN102901672B/en active Active
Also Published As
| Publication number | Publication date |
|---|---|
| CN102901672A (en) | 2013-01-30 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN102901672B (en) | Test method for researching transformation mechanism of martensite in austenitic stainless steel | |
| Berto et al. | High temperature fatigue tests of un-notched and notched specimens made of 40CrMoV13. 9 steel | |
| Han et al. | Constitutive equation and dynamic recrystallization behavior of as-cast 254SMO super-austenitic stainless steel | |
| Zhang et al. | Iron-based shape memory alloys in construction: research, applications and opportunities | |
| Arroyo et al. | Analysis of key factors of hydrogen environmental assisted cracking evaluation by small punch test on medium and high strength steels | |
| Derazkola et al. | Review on dynamic recrystallization of martensitic stainless steels during hot deformation: Part I—Experimental Study | |
| Glage et al. | Cyclic deformation behaviour of three austenitic cast CrMnNi TRIP/TWIP steels with various Ni content | |
| Fan et al. | Hot ductility and microstructure in casted 2205 duplex stainless steels | |
| Hwang et al. | Role of grain boundary carbides in cracking behavior of Ni base alloys | |
| Seifert et al. | Corrosion fatigue initiation and short crack growth behaviour of austenitic stainless steels under light water reactor conditions | |
| Rajput et al. | Physical simulation of hot deformation of low-carbon Ti-Nb microalloyed steel and microstructural studies | |
| De et al. | Effect of prestrain on tensile properties and ratcheting behaviour of Ti-stabilised interstitial free steel | |
| Dharavath et al. | Comparative study of ASS 316L on formability at room temperature and super plastic region | |
| Wang et al. | Arrhenius-type constitutive model for high temperature flow stress in a Nickel-based corrosion-resistant alloy | |
| CN110457834B (en) | Method for representing carburized steel carburized layer carbon concentration | |
| Xiong et al. | Tensile deformation temperature impact on microstructure and mechanical properties of AISI 316LN austenitic stainless steel | |
| Akita et al. | Some factors exerting an influence on the coaxing effect of austenitic stainless steels | |
| LAN et al. | A review of recent advance on hydrogen embrittlement phenomenon based on multiscale mechanical experiments | |
| Miao et al. | Investigation of low-cycle fatigue behavior of austenitic stainless steel for cold-stretched pressure vessels | |
| Zhu et al. | Fatigue crack growth behavior and fracture toughness of EH36 TMCP steel | |
| Mariappan et al. | A comparative evaluation of the effect of low cycle fatigue and creep–fatigue interaction on surface morphology and tensile properties of 316L (N) stainless steel | |
| Kannan et al. | Effect of sodium environment on the low cycle fatigue properties of modified 9Cr–1Mo ferritic martensitic steel | |
| Murty et al. | Nondestructive monitoring of structural materials using automated ball indentation (ABI) technique | |
| Wang et al. | Study of estimation of ductile-brittle transition temperature using U-notched small punch test specimens | |
| Jin et al. | Comparison of low cycle fatigue behavior of 304 stainless steels induced by tensile and torsional prestrain |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C06 | Publication | ||
| PB01 | Publication | ||
| C10 | Entry into substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant |